Re-timing cams separately for a 3.4L DOHC (especially on a Fiero)

BEFORE DOING THIS PROCEDURE:

1] Buy the GM manual for your year DOHC.

2] Buy the two tools recommended for the job.

3] Do a complete stock cam setting job--by the book.

4] Drive the car to verify it works.

NOW you can proceed with this excercise. This page does not claim to show you how to adjust your 3.4L DOHC cams. It just hopes to give you some ideas for things to try once you become an expert and know how to do this procedure as stock, and have had success with it. I also offer some solutions to pitfalls that occur with Fiero DOHC swaps, and also, helpful tips the manual does not cover. I will not be answering any questions about how to do a cam re-setting, outside of what this page covers.

Let's say you want to be able to set your intake and exhaust cams to different settings than stock. Maybe a bit of crank retard on intake cam, and even more for exhaust, to get some overlap to the intake. This actually takes a special tool I designed with Mike Matter's help. 

To try to align the intake and exhaust cams separately from each other is impossible using the GM cam alignment/hold-down tool--but the GM tool is important to own to find stock settings, and also, learn the procedure before trying this stuff..





First things first: before you go thinking you're going to put a wrench on the crank and turn the motor, pull the plugs.

 
 
 

But how to do that?? On a Fiero DOHC swap, with stock mounts, the firewall side is blocked from being able to be pulled fully out...

Undo your dogbone(s). Then undo the two rear cradle bolts while the rear is up in the air then just let the car down, sagging on it's struts--allowing the cradle to drop down, and the engine to lower itself in the bay.

 
 

but with my stiff suspension, this is never enough sag. the sparkplug wires still bang into the Fiero firewall lip.

 
 

I like to put a wide board on the jack, and support the Fiero's trunk, which is flimsy sheet steel, and lift the car up gently by the rear, leaving the cradle on the ground on the sagging wheels, and get some real clearance (pardon the camera's belt showing in the pic)

 
 

Even after lowering the cradle, clearance on the trunk side of the motor, next to the shock tower, is a big issue. You actually have to get the motor low enough to allow the sprocket tool, and a 3/8" drive breaker bar, or long ratchet in there, it IS tight....
(big hint: if you find a 1/2" drive ratchet and socket that works for this, more power to ya. I cannot fit anything but 3/8" drive stuff in there on a Fiero. And you best believe you WILL be using some breaker bar or ratchet at least 18" long--or a rather long metal tube around your regular-length ratchet wrench)."

Below is the stock Gm cam tool in place. It sets both the intake and exhaust cam flat.

next big tip: everything the GM manual says about white marks on the cam sprockets, or matching them up, for alignment, or anything like that--is B.S. If you have these two tools, and can figure out how to get the motor to TDC (refer to manual), you don't need any paint marks on the cogs. just forget you ever read that and read on...

The only thing the manual says about alignment that is interesting, is the notion of putting some vice grips on the cogs to hold them still while removing a whole cam carrier. we're not doing that. So don't worry about that right now.

You turn the Engine to TDC, loosen the bolts on both cams, and lock the cams down, then tighten the cam sprocket bolts--which--with that tool, ensures they are as flat as they'll ever get.
Then you remove the tool and use it on the other bank when you get around to TDC again (or use two tools). Can ONLY set the pair of cams together. Cannot do intake or exhaust separately. As Seven of Nine would say; "crude, but effective".

 
 

repeat after me: the cam-hold-down tool is NOT for holding sprockets while tightening bolts, too.

"the cam hold-down tool is NOT for holding sprockets while tightening bolts, too".

again!!!

"the cam hold-down tool is NOT for holding sprockets while tightening bolts, too".

Ok..... now you can go on... THIS is the tool you use to hold the sprockets still while you honk on them....

The GM cog-holding tool is equally important --it holds a cam cog still-- while untightening it's bolt, or re-tightening to the 80 ft lbs the manual calls for, without slipping the belt, or shredding it, or turning the crank while doing the job, and losing your place--or breaking your cam hold-down tool. My cog tool was getting bent while trying to use the dumb thing for what it was DESIGNED to do--work with a ratchet--so I welded it to a long and very useful steel handle and it is now sturdy as an ox. I suggest you do the same. If you don't weld, that's no excuse... go to a muffler shop and do it, whatever. 
The thing is a steaming piece of shit (despite it's utterly necessary nature).

 
 
 

I cheat a bit, I can do the cam re-timing with the timing belt cover still on. I cut out the plastic timing belt cover to allow the cogs to be fully exposed so the cog tool can grab them fully. Then I glued the cut-out portions (plus an extra lip) to the upper cam cog covers (using black RTV). When I remove the upper cog covers, I can now adjust my cams, w/o having to snake in there, and remove the whole black plastic cam belt cover, which I feel is a pain.

(yes that's a hole in the upper corner of the one on the left. A battle scar from when the motor mounts broke and the engine jumped around a bit. It's quite useful as a diagnostic window to see the condition and position of the belt. While not crucial, I'll probably never fix it)

 
 
 

It's important to be able to use the tool to hold a cam down, loosen the sprocket/cog, and then be able to turn the motor--which would turn the loosened cam sprocket independent of it's cam. Once you break the cam sprocket's bolt loose, you should coax the sprocket/cog loose --a bit-- by inserting something behind it, and yanking or tapping lightly on it. The first time the cog experiences this, it may be a bit tight to break the hold--and make a little "tink" noise ("tink" noise is optional).

 
 
 

So, below is the custom tool, doing it's thing. You find TDC for that bank, and can assume that for the most part, both cams are at flat. Which ever one you plan to adjust first, lock the custom tool down onto that one only (using the same style bolt as the GM hold-down tool), and loosen that sprocket. Turn the crank to the new position you want the cam to be at, and then tighten that cam sprocket back up. BE SURE to then remove the tool, before turning the crank any more.

This is some info for people who want to get inspired by this tool, and make thier own: The two bolts which face down, are machined flat where they meet the cam flat. They have lock bolts on them so you can use the regular GM tool ONCE....find flat with it, then adjust those two bolts to meet the cam flat, then lock both bolts into place. Yes, yes, it's possible to make a fixed tool of an exact length that hangs down and touches the cam flats, but what if (BIG if!!) the cam carrier's edges are not the same "hieght" from car-to-car, or...bank-to-bank??? That would sucketh great wind.

this shows the intake being adjusted first.

 

Of course, now, you get back to TDC, then hold down the exhaust cam, and loosen it. Adjust the crank to where you want your exhaust cam to be, and tighten that cam down. One bank down, one to go.

(Big hint: if you want to retard cam timing, move the crank past TDC--however far you wish--then lock the cam down. Opposite for crank advance, of course--set the cam slightly before the crank GETs to TDC.)
 

This may look a bit barbaric, but sometimes, when you are not doing both cams together, it may happen that you lose track of where flat IS on the cam. You can remove the custom hold-down tool, and gently grab the area around the cam-flat with a wide-open channel lock wrench and twist the cam a bit until it looks more or less right. Then put the tool back on and check it. Or you could use the GM tool, and reference both cams back to each other, by starting over to get a "stock setting" then work forward from there, using a custom tool like this.

 

I tried a little experiment and since my tool has a flat/square end, I tried scraping some lines into it, using a right-angle tool, and use the lines as a reference to try to eyeball if I am in in the ballpark for flat--when I lose track. You can wrench the cam back and forth, and get completely confused, sometimes. With the lines, when you stand the tool on the flats, you can see roughly which way it is not level, and use the wrench to adjust it the right direction. (this is not perfect, but helps some)